@MaskedSlime
They don't ignore them, just pace too slow, since it's just extras in tankoubons and they go from the very start (unlike anime, which skipped straight to the school). And that's a good thing, because it doesn't spoil anything beforehand, and manga would have been even more slower to progress (it would be now middle stratum at best), not to mention confusing. Two story lines work only in novel, and even then only for a little. After vol.5 Shun's side got abandoned, leaving at cliffhanger.
And anyway, Shun' story isn't interesting much and would work better either in a straight story, or at much slower pace, like manga, so they would eventually meet at some point.